Treatment of cellulosic textiles with strong hydroxide and acrylonitrile



Patented June 14, 1949 TREATMENT OF CELLULOSIC TEXTILES WITH STRONG HYDROXIDE AND AC- RYLONITRILE James W. Stallings, Atlanta, Ga., assignor to Riihm & Haas Company, Philadelphia, Pa... a

corporation of Delaware No Drawing. Application December 24, 1946,

Serial No. 718,267

This invention deals with the chemical modiflcation of cellulose yarns and fabrics to impart new and valuable properties thereto. More particularly, this invention relates to a process for imparting to cellulosic yarns and fabrics decreased moisture regain, decreased water absorbency, increased tensile strength, increased abrasion resistance, increased stiffness, altered dyeing properties, and a high degree of resistance to mildew.

It has previously been suggested to treat cellulosic yarns and fabrics with resinous condensates to increase stiffness and abrasion resistance. Such treatment relies upon the setting of resin within or on cellulosic materials, whereas the present invention is directed to an actual chemical modification of at least the surface layers of cellulose with new and surprising results. It has also been previously suggested to treat cellulose with caustic soda solution and acrylonitrile to increase the water-receptivity and water-absorbing properties thereof. This change in properties results from the formation of carboxyethyl groups in the cellulose molecule according to previously proposed procedures.

Now, unexpectedly, it has been found that properties which are almost the direct opposite of those previously obtained are developed by changing the conditions under which cellulosic yarns and fabrics are treated. According to the present invention, cellulosic yarns and fabrics are rendered less receptive and absorbent to water, stronger, stiffer, and more abrasion-resistant than the usual cotton, rayon, or linen yarns or fabrics of the art by impregnating cellulose in the form of yarn or fabric with an aqueous solution of a strongly alkaline hydroxide, removing excess solution from the impregnated cellulose, immersing the thus-treated cellulose in a solution of acrylonitrile in an inert, water-immiscible organic solvent for a time suflicient to react acrylonitrile and cellulose, and removing acrylonitrile and any alkalinity remaining in the treated cellulose. The treatment with alkali solution is best performed while the yarn or fabric is held under tension. The subsequent steps may be performed with or without tension, as desired.

In spite of tension, the diameter of treated yarn or the thickness of treated fabric increases. The treated product increases in stiffness more or less in proportion to the amount of acrylonitrile reacted with the cellulose. This is also true of the absorption and retention of dyes which are ordinarily used only on silk and wool. When about 0.3 to 0.9 cyanoethyl group on the average 3 Claims. (Cl- 8-1162) is added per glucose unit, corresponding to a nitrogen content of about 2.5% to about 6%, the product is particularly responsive to silk dyes. When one or more cyanoethyl groups per cellulose unit are introduced, the product responds well to wool dyes.

The behavior of the treated yarns or fabrics toward liquid ammonia provides an index of the extent of reaction of cellulose with acrylonitrile where there is no opportunity for the nitrile group to be hydrolyzed. With a nitrogen content up to about 6%, the treated cellulose is not particularly attacked by liquid ammonia. At a nitrogen content of about 9%, there is some attack by ammonia, but the treated cellulose will not dissolve. When more than two cyano groups on average have been introduced per cellulose unit (corresponding to a nitrogen content of over 10.5%), liquid ammonia. acts as a solvent. For optimum finishing effects on yarns or fabrics, it is desired to introduce not over about 10% of nitrogen into the cellulosic yarn or fabric, preferably 2.5% to 10% of nitrogen, a state which may be determined by a test with liquid ammonia. The nitrogen content and behavior toward liquid ammonia provide, therefore, criteria for, determining how far the reaction between cellulos and acrylonitrile has been carried for purposes of this invention. In the preferredrange, there are introduced from about 0.3 to less than two cyanoethyl groups per glucose or cellulose unit. Within these limits/the desired properties are attained and the form of the cellulose'yarn or fabric remains intact.

As cellulosic material there may be used yarns or fabrics made of'cotton, linen, ramie, or regenerated cellulose, or mixtures of these materials, or purified wood cellulose fibers. Fibers may be treated in the form of webs, felts, or battimes, as well as in the form of woven or knitted fabrics.

As a solution of alkaline hydroxide, there may be used solutions of a strong hydroxide, such as sodium hydroxide, potassium hydroxide, or other .hydroxide of the alkali metals, or a strong quaternary hydroxide, such as .benzyl trimethyl quaternary ammonium hydroxide or dibenzyl dimethyl quaternary ammonium hydroxide, varying in concentration from 10% to 30%. The prefeet is desired. Durin impregnation, the strong hydroxide forms alkali cellulose in part.

After impregnation, excess solution is removed by squeezing, centrifuging, slot-extracting, or equivalent operation, until the gain in weight of the impregnated yarn or fabric is about equal to the weight of the dry yarn or fabric. Impregnating followed by removing of excess solution leaves about 85% to 110% of solution in the yarn or fabric, based on the dry weight thereof. These operations may be performed in the case of yarn with packages through which the solution is pumped. Fabrics may be handled in a frame or tenter. After excess solution has been removed, the alkali-impregnated cellulose may be stored for a time, preferably in a tight container which prevents free circulation of air.

After the cellulosic material has been impregnated with a solution of a strong hydroxide and the excess thereof has been removed, it is immersed or soaked in a solution of acrylonitrile in an inert, water-immiscible solvent. tration of acrylonitrile may be varied from 5% up to about 50%. As inert solvent, there is preferably used a hydrocarbon such as a petroleum distillate, solvent naphtha being particularly useful, or an aromatic solvent, such as benzene, toluene, or xylene, or a solvent such as cyclohexane or methylcyclohexane, or mixtures of such solvents. The solvent should not only be inert toward acrylonitrile, but it should also be capable of readily volatilizing at temperatures from room temperature up to temperatures which are readily reached in low-pressure steam-heated driers (l00-120 C.).

The treatment of impregnated yarn or fabric with the solution of acrylonitrile is performed at temperatures between 0 and 35 C. Treatment is continued until a particular property is developed to the desired or required extent as a. result of reaction of acrylonitrile with cellulose. The amount of acrylonitrile reacted and the number of nitrile groups introduced are approximately proportioned to the time of treatment and also depend in part upon concentration and temperature.

Thus, the nitrogen content was found to vary in in case in which a cotton fabric was impregnated with a aqueous sodium hydroxide solution and later soaked in a 20% acrylonitrile solution in solvent naphtha from 2.5% of nitrogen after one hours immersion to about 9% after immersion for twenty-four hours. The material after one hour had developed noticeable stiffness, had increased in thickness, had decreased in absorptivity for water, and had acquired other properties discussed above. These properties became more marked as the extent of reaction progressed.

After the reaction has proceeded for one to twenty-four hours, it is interrupted. This may be done by displacing the solvent solution and washing away free strong hydroxide in the treated yarn or fabric or by neutralizing or acidifying the treated yarn or fabric. A dilute solution of an acid, such as acetic, formic, lactic, hydrochloric, or other acid, may be used; or there may be used an acid salt, such as an acid fluoride, often applied as a sour in laundering. The acid is then thoroughly rinsed away and the yarn or fabric dried. It may be subjected to a dyeing or other finishing operation, including application of softening agents, such as a sulfonated oil or tallow or a long-chained quaternary ammonum salt, or it may be given a mechanical treatment such as calendering or button-breaking.

4 This invention is further illustrated by the following examples.

Example 1 An 80 x 80 cotton sheeting held in a frame was padded through a aqueous sodium hydroxide solution. Excess solution was removed by squeeze The concen- 76 in proportion to nitrogen content.

rolls until the increase in weight did not exceed the dry weight of the fabric. The cloth was then immersed in a 10% solution of acrylonitrile in Stoddard solvent for sixteen hours. It was then thoroughly washed in water, passed through a dilute acetic acid solution, and washed with water until neutral. The washed fabric was dried in an oven at 220 F. for thirty minutes.

After samples of this treated fabric had been conditioned for twenty-four hours, they were evaluated by various tests and measurements and compared with samples of the original fabric. Thickness was found to be 0.0114 inch compared to 0.0088 inch for the untreated fabric. Tensile strength of warp was sixty pounds (for one-inch strips) compared to 43.4 pounds for untreated strips; strength of filling was 42.1 pounds compared to 32.8 pounds. Elongation at break was 7.2% as against 9.6% for the untreated fabric. Air permeability by a standard penetrometer was 68.7 cubic feet per square foot per minute compared to 98.7 cubic feet per square foot per minute for the untreated fabric. Abrasion resistance had increased from 7650 revolutions in the T. B. L. test to 45,250. Moisture regain was 3.9% for the treated cloth compared to 5.6% for the untreated. Water absorbency was 30% as compared to 60%. Stiffness, as measured by the Gurley Stiffness Tester, increased from 4.3 milligrams to 87.6 milligrams. Nitrogen content was 9.39%, corresponding to introduction of 1.7 nitrile groups per anhydroglucose unit. The treated fabric took up both silk and wool dyes. 7

Pieces of treated fabric were buried in soil along with pieces of untreated fabric and samples of fabric impregnated with 0.3% of copper naphthenate. The untreated cloth was completely disintegrated in a week. The copper-treated pieces removed at the end of four weeks had lost 40% of their original tensile strength. The fabric treated as above described, however, showed a high degree of mildew resistance and had not lost in tensile strength.

Example 2 A 48 x 48 cotton muslin was passed in a frame through an aqueous 15% sodium hydroxide solution. Excess solution was expressed by rolls. The cloth was then passed into a solution containing 20% of acryonitrile in an aromatic petroleum naphtha of high kauri-butanol number. At hourly intervals pieces of the treated fabric were removed from the solvent solution and immersed in denatured alcohol saturated with sulfur dioxide. They were washed with a 10% hydrochloric acid solution and then with water.

Nitrogen analyses were made by the Kjeldahl method with samples of each piece. Nitrogen contents were found, as follows: After one hour, 2.50%; two hours, 4.37%; three hours, 5.12%; four hours, 5.72%; seven hours, 6.06%; and twenty-four hours, 8.89%.

Samples dyed with silk dyes were deeply colored. The samples with relatively high nitrogen contents were highly receptive to wool dyes. While liquid ammonia did not actually dissolve any of the hourly taken samples, this reagent caused slight swelling of the modified cellulose Thickness,

stiffness, abrasion resistance, and tensile strength increased. Moisture and water absorption decreased. Thread count remained practically th same as in the original piece of cloth.

I claim:

1. The process of increasing abrasion resistance, stiffness, and tensile strength and decreasing moisture absorptivity of cellulosic yarns and fabrics which comprises impregnating said cellulosic material with a 10% to 30% aqueous solution of a strong hydroxide at to 30 C., removing excess solution therefrom until the gain in weight is about equal to the dry weight of the dry cellulosic material, immersing the impregnated material in a to 50% solution of acrylonitrile in an inert water-immiscible organic solvent at 0 to 35 C. for one to twenty-four hours, separating material and solution, and removing acrylonitrile and strong hydroxide remaining in the treated material.

2. The process of increasing abrasion resistance, stiffness, and tensile strength of cellulosic yarns and fabrics and decreasing the water and moisture absorptivity thereof which comprises impregnating cellulosic yarn and fabric while under tension with a to 20% aqueous solution of a strong hydroxide at 0 to 30 0., removing excess solution therefrom until the weight of solution remaining in the impregnated cellulosic material equals approximately the weight of the dry untreated material, immersing the thus-impregnated cellulosic material at 0 to 35 C. in a 10% to 20% solution of acrylonitrile in an inert volatile hydrocarbon solvent for one to twentyfour hours, separating material and solution, neutralizing any strong hydroxide remaining in the treated material, and removing acrylonitrile solution therefrom.

3. The process of increasing abrasion resistance, stifiness, and tensile strength of cotton in the form of yarns and fabrics and decreasing the water and moisture absorptivity thereof which comprises impregnating cotton in said forms while under tension with a 10% to 20% aqueous solution of sodium hydroxide at 0 to 30 C., removing excess solution therefrom until the cotton holds approximately a weight of solution equal to the dry weight of the untreated cotton, immersing the thus-impregnating cotton at 0 to C. in a 10% to 20% solution of acrylonitrile in an inert volatile hydrocarbon solvent for one to twenty-four hours, separating cotton and solvent solution, neutralizing any sodium hydroxide remaining.in the cotton, and removing the acryionitrile solution therefrom,

JAMES W. STALLINGS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS I Number Name Date 2,233,475 Dreyfus Mar. 14, 1941 2,375,847 Houtz Mar. 15, 1945 2,390,032 stallings i. Nov. 27, 1945 

